1. Field of the Invention
The invention relates to a safety device for a power circuit and a fuse box effectively adapted for the safety device. The power circuit supplies power to loads on two related systems. The loads include, for example, an actuator and an electrical control unit (referred to as ECU) for controlling the actuator.
2. Description of Relevant Art
A conventional energization system for a 14 V-system automotive includes a junction box. The box includes a branched power circuit. The system includes ECUs. The system includes loads for producing physical output, such as an actuator. The power circuit supplies a current to the ECUs and actuators through common fuses. The system allows a voltage from a power supply to be directly inputted to the ECUs. Respective ECUs include corresponding series regulator inside them, which converts to a low-voltage of, for example, 5V for actuating an internal circuit.
With recent advances in development, an automotive is equipped with a motor generator with efficient fuel cost, and can drive at a high-voltage of 42 V. Voltage conversion of a high-voltage of 42 V, using a series regulator, causes excessive loss. A proposal is that all ECUs house more efficient switching converters. The proposal, however, would result in remarkably high prices.
Another proposal is that a junction box includes a DC/DC converter within it. The converter collectively converts the voltage of a 42 V power supply into a lower voltage of 12 V to be distributed to respective ECUs. One system includes a power circuit for a high-voltage, which applies a voltage of 42 V to an actuator. Another system includes a power circuit for low-voltage, which applies a voltage of 12 V to an ECU. Respective power circuits have corresponding fuses for high and low voltage in them to protect the circuits.
As the ECU controls the actuator, the two systems are closely related to each other. If an abnormality occurs on one system when a current is being supplied to loads on the two systems, the supply of current to the other system is necessarily stopped.
In the 14 V system, a current is supplied to both of the actuator and ECU through fuses. For example, in response to an abnormality in the actuator, fusion of a fuse automatically stops the supply of a current to an ECU. In response to an abnormality in the ECU, fusion of a fuse automatically stops the supply of current to the actuator. These produce no specific problems.
Another proposal is that energization system is separated into systems for the actuator and the ECU respectively. A current is supplied to each of the actuator and the ECU through corresponding fuses for high and low voltage. The fusion of one fuse in the system due to an abnormality allows the other fuse to be left effectively, and to continuously supply a current to the other load.
When a fuse fuses if an abnormality exists on, for example, the actuator, the supply of a current to the ECU for controlling it should stop. After the fusion of one fuse, a voltage is continuously applied to the remaining load. The application can cause an abnormality on the remaining system, such as a rapid short-circuit or a rare-short. Systems separated from a power circuit produce new problems.
The invention is directed to a safety device for a power circuit, and a fuse box effectively adapted for the safety device. Where a current is applied to two related loads of two systems, the fusion of the fuse on one system caused by the fusion of the fuse on other system ensures the safety of entire circuit.
A first aspect of the invention is directed to a safety device for a power circuit. The device includes a first power circuit including a first load and a first fuse element for receiving a first voltage power from a power supply to supply the first voltage power to the first load through the first fuse element. The device includes a second power circuit including a second load and a second fuse element for receiving a second voltage power from a converter, which converts the first voltage power into the second voltage power, to supply the second voltage power to the second load through the second fuse element. The device includes a fusion system for fusing the other of the first and second fuse elements when an arbitrary one of the first and second fuse elements fuses.
Preferably, the fusion system includes a circuit for applying overcurrent to the other fuse element to be fused when said arbitrary fuse element fuses.
Preferably, the fusion system includes a heating element for heating the other fuse element to be fused at a fusion temperature when said arbitrary fuse element fuses.
Preferably, the first power circuit includes a first power terminal connected to the power supply. The first power circuit includes a second load terminal connected to the first load. The second power circuit includes a second power terminal connected to the power supply. The second power circuit includes a second load terminal connected to the second load. The first fuse element includes a first fusible member extending from the first power terminal. The second fuse element includes a second fusible member extending from the second power terminal. The fusion system includes a first conductive member extending from the first load terminal, and conductively contacting with the first fusible member. The fusion system includes a second conductive member extending from the second load terminal, and conductively contacting with the second fusible member. The fusion system includes a displacing system for displacing a corresponding conductive member to contact with the other fusible member, the other conductive member or the other load terminal, when said arbitrary fusible member fuses.
Preferably, the second load includes a controller for controlling the first load.
Preferably, the second power circuit supplies a current to the controller, serving as a power circuit for low-voltage. The first power circuit supplies a current to the first load, serving as a power circuit for high-voltage.
Preferably, the first fuse element includes a first fusible member arranged side by side with a first circuit member of the first power circuit. The second fuse element includes a second fusible member arranged side with by side a second circuit member of the second power circuit. The fusion system includes a first conductive member having a tendency to deform to contact with the second circuit member. The first conductive member is separated away from the second circuit member, and is retained against the first fusible member. The fusion system includes a second conductive member having a tendency to deform to contact with the first circuit member. The second conductive member is separated away from the first circuit member, and is retained against the second fusible member.
Preferably, the fusion system includes a first shunt circuit between the first fuse element and the first load for grounding the first power circuit. The fusion system includes a control circuit responsive to identical electric potentials of both terminals of the second fuse element to open the first shunt circuit.
Preferably, the control circuit is responsive to an electric potential difference between both terminals of the second fuse element to close the first shunt circuit.
Preferably, the fusion system includes a second shunt circuit between the second fuse element and the second load for grounding the second power circuit. The fusion system includes a control circuit responsive to identical electric potentials of both terminals of the first fuse element to open the second shunt circuit.
Preferably, the control circuit is responsive to an electric potential difference between both terminals of the second fuse element to close the first shunt circuit.
A second aspect of the invention is directed to a fuse box adapted for power circuits. The fuse box includes a first power terminal configured to connect a power supply via a first power circuit. The fuse box includes a first load terminal configured to connect a load of the first power circuit. The fuse box includes a second power terminal configured to connect the power supply via a second power circuit. The fuse box includes a second load terminal configured to connect a load of the second power circuit. The fuse box includes a first fusible member extending from the first power terminal. The fuse box includes a second fusible member extending from the second power terminal. The fuse box includes a first conductive element extending from the second load terminal, and conductively contacting with the first fusible member. The fuse box includes a second conductive member extending from the second load terminal, and conductively contacting with the second fusible member. The fuse box includes a displacing system for displacing a corresponding one of the first and second conductive members to contact with the other fusible member, the other conductive member or the other load terminal, when an arbitrary one of the first and second fusible members fuses.
Preferably, said corresponding conductive member has resilience.
Preferably, the displacing system includes a resilient member biasing said corresponding conductive member against said arbitrary fusible member.
According to the safety device, when one of the first and second fuse elements fuses, the other fuse element is forced to fuse, thus stopping current to the other load. Thus, if an abnormality occurs on one of the first and second loads in association with each other, continuous supply of a current to the other load would produce inconvenience. The device securely prevents this inconvenience and ensures safety.
For example, one of two loads is an actuator and the other load is a control unit for controlling the actuator. If an abnormality on the actuator causes a fuse to be fused, this device prevents continuous application of current to the control unit. Similarly, if an abnormality on the controller causes the other fuse to be fused, the device prevents continuous application of current to the actuator.
For example, a combination of logical circuit ensures the safety of the power circuits.
For example, a combination of the heating element and the circuit for energizing the heating element ensures the safety of the power circuits.
According to the device, an abnormality on the first load causes the application of overcurrent to the first power circuit to fuse the first fusible member. The fusion disengages the retention of the first fuse element in a normal position. The first conductive member is displaced toward the second fusible member, the second conductive member, and the second load terminal for conductive contact.
Thus, the second fusible member is joined with the first load, as well as with the second load. The joint allows the instant application of overcurrent more than normal to the second fusible member. The overcurrent fuses the second conductive member, which simultaneously stops the energization of both loads, thus ensuring safety.
If an abnormality occurs on the second load, the fusion of the second conductive member allows the fusion of the first conductive member in a reversed motion. Similarly, this simultaneously stops the energization of both loads, thus ensuring safety.
If the controller has an abnormality when the second fuse element for energizing the controller fuses, the energization of the first load to be controlled by the controller stops. On the other hand, if the first load has an abnormality when the first fuse element for energizing the first load fuses, the energization of the controller stops. This ensures safety of the entire energization system.
If one of the first and second fuse elements of the first and second power circuits fuses due to an abnormality, the other fuse element is securely fused. The fusion prevents an unforeseen situation, such as the generation of overcurrent or a rare short-circuit.
According to the fuse box, when the application of overcurrent to the first power circuit allows the fusion of the first fusible member, the fusion disengages the retention of the first conductive member at a normal position. The first conductive member is displaced toward the second fusible member, the second conductive member or the second load terminal for conductive contact. Thus, overcurrent more than normal is instantly applied to the second fusible member. The overcurrent fuses the second conductive member, stopping the energization of the load, and thus ensuring safety. When the application of overcurrent to the second power circuit allows the fusion of the second fusible member, in a reversed motion, the fusion of the first fusible member stops the energization of the load, ensuring safety.
One of the first and second fusible members is fused, and the corresponding conductive member in conductively contact with said one fuse element conductively contact with the other fuse element by its own resilience. Thus, compared to using another spring separated from a conductive member, this reduces the number of components and simplifies the structure.